COLONIE — Sandra Beth Geisel, the former Christian Brothers Academy teacher accused of having sex with a 16-year-old pupil, weighs a plea bargain offer, according to those familiar with the case.

Geisel, indicted earlier this month on charges of third-degree rape and engaging in a sex act for seducing the teen during three periods in May, has been offered a plea bargain by the Albany County district attorney’s office and could accept it during a court appearance hastily scheduled for yesterday.

If convicted of the charges at trial, Geisel would have to serve up to four years in state prison on each count. But the New York Post reported on Saturday that the plea offer could cut her time to less than a year in local jail.

The plea deal was hammered out between Geisel’s attorney, prosecutors and County Judge Stephen Herrick. Geisel was arrested on Aug. 1, then released on bail. She has been in jail since an unrelated drunken-driving arrest on Aug. 19. The time she has spent behind bars would be subtracted from whatever time she eventually has to serve.

The district attorney’s office sent out an unusual media advisory last week, alerting reporters that Geisel would be in court today and promising “there is a possibility that this office will have something to say about the case shortly thereafter.”

Richard Arthur, a spokesman for District Attorney David Soares, said on Sunday, “What I can say is, ‘You don’t want to miss it.’ ”

“We have a conference and that’s it,” Geisel’s attorney, Donald Kinsella, said.

Geisel is suspected of having sex with two other CBA students, but at the time they were both 17, the age of consent in New York. She was fired in June, shortly after Cohoes police allegedly caught her with one of the students.

The charges against Geisel include claims that she had sex with the student at her Colonie home on May 15, at his Ravena home on May 26 and 27 and in the overnight hours between May 28 and 29 at the school’s athletic field press box.